1. Conventional X-Ray Apparatuses and Methods
It is well known that the use of x-rays is vital in the treatment and diagnosis of patients, especially in chiropractic care. The effectiveness of radiographic diagnosis is critically dependent on the accuracy and quality of the x-ray images, which depend on the proper positioning the subject patient. The more precise the patient is aligned with the x-ray, the better is the resulting image. As such, the effectiveness of radiographic diagnosis is often compromised because it can be difficult to get the patient in just the right position and to orient the x-ray machine accordingly to take clear x-ray images.
Generally, an x-ray apparatus is comprised of an x-ray generator (commonly known as an x-ray tube) and a receptor (typically comprising a film cassette inserted in a grid cabinet, though recent technology has allowed for the images to be digitally captured).
The x-ray tube generates a beam that is projected onto the subject patient, who is interposed between the generator and the receptor. A collimator, which is a device that narrows the beam for improving the resolution of the x-ray image, is commonly used to collimate the beam to the proper size field of the patient's area of diagnostic interest. To further reduce the scatter associated with x-rays and produce a clearer image, a grid is used to block random rays and allow only rays generally in direct line to reach the film. Most importantly, it is imperative that the patient is properly positioned in alignment with the generator and the receptor to enable clear and accurate images of the patient's bones (or other diagnostic areas) to captured on the film.
2. The Use of X-Rays in Chiropractic Care
In chiropractic, subluxation is a physical misalignment that distorts the body, causing the spine to deviate from its normal position, which can result in pain and ailment throughout the whole body. To restore balance, evaluation and adjustment to the upper cervical is often necessary. As opposed to adjustments of the entire spinal column, specific adjustments can be made to the first cervical vertebra to bring it back to its proper position. The first cervical vertebra (also known as the atlas or C-1) is the topmost bone in the spine, being the first of the seven vertebrae in the spine known as the cervical spine (C spine).
Upper cervical adjustment depends upon precise biomechanics. This requires 3D composite x-rays to measure specific spinal misalignment in order to determine how best to adjust and correct it. Precisely taken x-rays are thus a critical part of ensuring the spinal correction is accurate and successful. Proper X-ray positioning is therefore essential to patient care.
In this regard, several cervical views are generally necessary for analysis of the upper cervical, including: lateral, base posterior, vertex, and nasium. From these x-ray views, a precise analysis of the position of the atlas vertebra is used to determine a vector for its adjustment.
This section will describe the radiographic views and how patients are currently positioned for these views.
A lateral cervical view is a side view of the upper cervical spine, taken to determine the relationship of the C-1 vertebra to the mastoid and to measure the atlas-plane-line angle (or “S-Lline” for taking a nasium film as described below). To take an x-ray in a lateral view, the patient is positioned with his shoulder against the lower part of the grid cabinet (also known as the bucky). Prior to positioning the patient for this view, the positions of the patient's ears are recorded against a horizontal line chart to determine the patient's head tilt as a component of his subluxation. The patient's chin is tucked so that the external auditory meatus is parallel to the inferior orbit, with the infra-orbial meatal line being parallel to the floor. The patient is then rotated using the movable chair in which he sits so that the head is perpendicular to the x-ray source. If the patient has an excessive head-tilt as determined using the horizontal line chart, the bucky and tube must also be tilted at the same angle, so the head remains lateral on the film. A string is used to make sure the tube is at the proper angle. The string is passed at the bottom of each earlobe when it is at the proper angle. The bucky is adjusted to correspond to the number of degrees the tube is tilted to give a true lateral position for the head in the horizontal plane on the resulting film. The central ray is centered to the area between C-1 and C-2 and the bucky is centered to the central ray. The patient's ears are aligned using the glabella bar and head clamps are applied to secure the patient. As setup, an x-ray image of the lateral cervical is taken.
A base posterior film is used to visualize the upper cervical spine from the “bottom up” point of view, in which the foramen magnum (occiput), atlas, and axis are seen as consecutive superimposed rings. The patient is seated facing the x-ray tube. The grid cabinet is tilted downward to a specified angle and positioned so that its center is perpendicular to the patient's vertex (the very top of the head). The tube is tilted upward and positioned so that the central ray coincides with the center of the film. This film is used to visualize the orientation and shape of the occipital condyles, the size and shape of the foramen magnum, the rotational angles of atlas and axis, and perhaps the severity of any existing constriction of the neural canal resulting from misalignment of atlas and/or axis.
A vertex film is analogous to the base posterior film described above except that the x-ray beam traverses the skull in the opposite direction. The patient is positioned facing the grid cabinet which is tilted upward to a specified angle. The patient's chin is made to settle on a special chin-harness that is attached to the grid cabinet. With the bucky thus angled, the patient's chin is elevated so there is a 90° relationship between the angle of the mandible and the sternocleidomastoid muscle. The tube is moved to a caudal angle so that the central ray is perpendicular with the floor of the skull at the atlas traverse process. The central ray is directed at right angles through a line passing from the patient's superior orbit to the tip of the transverse process, the angle of which is verified by using a string. In other words, the x-ray tube is raised above the patient's head and angled downward so that the central ray traverses through the patient's vertex and coincides with the center of the film. The vertex view is taken to produce a clear view of the atlas, nasal septum and C-2 spinal canal to determine atlas rotation and C-2 spinal canal rotation.
The purpose of a nasium film is to obtain an optimal view of all the structures at the proper angle and exposure so as to enable accurate film analysis. To take a nasium film, the atlas has to be properly positioned on the film by measuring the S-line off lateral and finding the landmark for C-1 so that the central ray is at the proper angle. The goal of this positioning effort is to visualize atlas precisely “head-on” therefore the tube is tilted to an angle that is perpendicular to the atlas plane line angle measured on the lateral film. Accordingly, the proper S-line is determined from the lateral cervical film. Next, the correct orientation of the atlas transverse process (atlas TP) is determined so that the atlas can be properly positioned on the film. With the patient facing the tube, the bucky is tilted so that it is at the same approximate angle as the back of the head and shoulders. The patient's head is positioned approximately in the center of the bucky. The tube is angled so that the central ray will travel along the S-line and will exit the patient at the level of the atlas transverse process. The central ray must enter the film ½ inch above its center. A string is extended from the tube to the bucky where the central ray will hit the bucky so as to make sure that the patient's head is correctly oriented and that the central ray is consistent with the S-line. With the head secured by clamps, the nasium film is taken.
An APOM (anterior to posterior open mouth) film is used to visualize the upper cervical spine from the anterior to posterior point of view. The patient is positioned with the back of his head against the grid cabinet. The x-ray tube is positioned at a specific distance from the grid cabinet and the central ray of the x-ray beam is aimed so that it intersects the level of the C1 vertebra. The film is captured (with the patient open-mouthed) to get a clear shot of the upper cervical spine to assess atlas and axis laterality as well as to discern any anatomical abnormality or trauma.
Current radiographic methods for chiropractic diagnosis, particularly of the upper cervical spine, based on taking the x-ray views described above, suffer from inaccuracies due to the subjective positioning of the patient from view to view. This results in radiographic images that can be inaccurate or unclear. Because upper cervical adjustment depends upon precise biomechanics, a system and method are needed to objectively and precisely position patients in respect to the different radiographic views described above.
Further, current radiographic methods of the upper cervical spine are based on using x-rays to determine static misalignment of the vertebrae, rather than determining restrictions in the motion of the cervical vertebrae which can only be discerned by taking range-of-motion radiographs. That is, such traditional radiographic methods for determining chiropractic listings of the upper cervical spine characterize misalignments based on films in the neutral position. These methods do not consider active biomechanical dysfunction. Understanding that the most accessible component of the subluxation complex is articular fixation, a new method that characterizes fixation based on dysfunction would improve confidence in the listing attained and the quality of the care delivered.